The present invention relates in general to lamp assemblies especially suitable for vehicle mounting, and more particularly to shock mounting of incandescent lamp bulbs with the bulb base mounted in a horizontal position to provide protection against impact and vibration.
Vehicle mounted lamp assemblies have for a long time been plagued with the problem of filament failure because of repetitive shock loading of the lamp assembly. Because of the frequent vibration and mechanical shocks, the lamps, especially on road vehicles, may fail quite rapidly and require frequent replacement.
For many years, shock mountings devised for reducing the shock forces imposed on bulb filaments involved considerably expensive arrangements from both the manufacturing and installation standpoint. While prior shock mountings were effective to a certain degree, they were not satisfactorily able to cope with impulse forces applied in certain directions to the lamp assemblies.
Various methods have been previously used for shock mounting of bulbs for vehicular use.
Among the techniques previously employed for attempting to reduce shock damage to lamps was the provision of metallic springs providing resilient suspension for the lamp bulbs, typical of which are the Gross U.S. Pat. No. 2,504,327, the Williamson U.S. Pat. No. 2,051,324 and Yost U.S. Pat. No. 1,948,690. However, such metallic spring suspension arrangements have little damping action. Elastomeric suspensions have also been used, but these have poor centering force and some elastomeric materials are susceptible to the high temperatures encountered, particularly in automotive head lamp application. The critical optics of head lamps and some other signalling lamps, require that the bulb filament be held precisely on the focus. If the bulb is displaced by impact or vibration it must return to design focus when the disturbing force is removed. The focus is fixed by design, but manufacturing variations in the lamp and the bulb make it difficult to reconcile the design focal point with the acutal focal point without some means of adjustment. In many prior art arrangements, the elastomeric bands or performed or molded elastomeric sockets and metallic spring systems have the undesirable property that when the lamp and suspension are at rest, the position of the bulb filament relative to the focus of the optical system is not easily adjustable.
The use of a plastic mounting with two sinusodal or substantially S-shaped bands or arms with pivoting ends and a vertically oriented bulb has been disclosed in the earlier Baldwin U.S. Pat. No. 3,327,110, reissued as U.S. Pat. No. Re. 30,498. However, the lamp bulb is this arrangement is potted with its base in the vertical position, rather than a horizontal position, and it is difficult to provide focusing of the bulb filament with respect to the lamp's optical system.
An object of the present invention is the provision of a novel shock mount for lamp bulbs, particularly for automotive or truck vehicle applications, specifically designed for horizontal oriented bulbs to offer resiliency in all planes of movement and to have a sufficiently strong centering force to ensure that the bulb will return to the proper focus after being disturbed by vibration or impact.
Another object of the present invention is the provision of a novel shock mount as described in the immediately preceding paragraph, which employs a three arm design with three horizontal pivots arranged in a triad to offer convenient means for adjusting the position of the bulb filaments in order to compensate for manufacturing variations in the bulb and optical system of the lamp.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.